US3991329A - Touch-operation switch - Google Patents

Touch-operation switch Download PDF

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Publication number
US3991329A
US3991329A US05/546,138 US54613875A US3991329A US 3991329 A US3991329 A US 3991329A US 54613875 A US54613875 A US 54613875A US 3991329 A US3991329 A US 3991329A
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United States
Prior art keywords
touch
terminals
transistor
negative resistance
operation switch
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US05/546,138
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English (en)
Inventor
Hitoo Iwasa
Gota Kano
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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Publication date
Application filed by Matsushita Electric Industrial Co Ltd filed Critical Matsushita Electric Industrial Co Ltd
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Publication of US3991329A publication Critical patent/US3991329A/en
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
    • H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
    • H03K3/353—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of field-effect transistors with internal or external positive feedback
    • H03K3/356—Bistable circuits
    • H03K3/3565—Bistables with hysteresis, e.g. Schmitt trigger
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
    • H03K17/96—Touch switches
    • H03K17/962—Capacitive touch switches

Definitions

  • This invention relates to a touch-operation switch, which switches by only a slight touching to a touching elecrode by a human body.
  • touch-operation switches are practically and widely used in electric appliances or electric machines, for instance, in electric fans or electric centrifugal dehydrators, in order to stop their operation for securing safety against inadvertent touches by a human body.
  • touch-operation switches have been constituted in a manner that the switch detects the proximity or a touch of a human body by means of capacity change due to electrostatic induction, or that the switch detects a change of a weak electromagnetic field due to human proximity or a touch.
  • Such conventional touch-operation switches pick up input signals of very small level, and therefore are liable to false operations due to noise. In order to eliminate such false operation, conventional touch-operation switch necessitates a complicated noise-resistant detection circuit.
  • the present invention provides a novel and simple but reliable touch-operation switch of fully semiconductorized type.
  • FIG. 1 is a circuit diagram of one example embodying the present invention.
  • FIG. 2 is a circuit diagram showing electrical connection of a negative resistance device 2 employed in the circuit of FIG. 1.
  • FIG. 3 is a graph showing relation between the voltage across the two terminals and the current from one terminal to the other terminal of the negative resistance device used in the touch-operation switch of the present invention.
  • FIG. 4 is a circuit diagram of one example of a burglar alarm bell system employing the switch of FIG. 1.
  • a negative-resistance device 2 for use in the apparatus of the present invention is elucidated referring to FIG. 2.
  • FIG. 2 shows a circuit example as disclosed in prior art, for example IEEE transactions on Circuit Theory, March 1963, page 25-35 and Proceedings of the IEEE, April 1965, page 404.
  • the negative resistance device 2 comprises complementary connection of an n-channel junction type field-effect transistor 21 and a p-channel junction type field-effect transistor 22, connected to each other as shown by source S1 to source S2, or their output circuits may be alternatively serially connected from drain to drain, or source to drain, in any case, and each gate is connected to the remaining drain or source of the opposite field-effect transistor.
  • the gate electrode G1 of a depletion mode n-channel junction type FET 21 is connected to the drain electrode D2 of a depletion mode p-channel junction type FET 22, and the gate electrode G2 of the p-channel type FET 22 is connected to the drain electrode D1 of the n-channel type FET 21.
  • Both source electrodes S1 and S2 of both FETs 21 and 22 are further series-connected to each other.
  • the current I increases showing positive resistance characteristic as the voltage increases, but the current also shows gradually a saturation characteristic, and after the current exceeds the voltage of the peak current point m (i.e., the first threshold voltage Vt1), namely, in the region between Vt1 and Vt2, the current declines as the voltage increases, showing a so-called negative-resistance characteristic. Finally, when the voltage exceeds the second threshold voltage Vt2, the current I enters the cut-off state. This cut-off state of the current continues until the voltage reaches a break-over voltage Vt3 where one of the FETs begins to break-down. When the voltage passes over the Vt3 point, a break-down current is produced.
  • the first stable region of 0 ⁇ V ⁇ Vt1 there are the first stable region of 0 ⁇ V ⁇ Vt1, and the second stable "OFF" region of Vt2 ⁇ V ⁇ Vt3, and the unstable state lies in the applied voltage range of Vt1 ⁇ V ⁇ Vt2.
  • FIG. 1 is a circuit diagram of one example of a touch-operation switch of the present invention.
  • a D.C. power source E an impedance, for instance, a resistor 3 and collector-emitter circuit of a bi-polar transistor 1 is connected in series, and a push-button resetting switch 5 which closes during a pressing is connected across the resistor 3, a semiconductor negative resistance device 2 of abovementioned type is connected across the base and collector of the transistor 1, a touching electrode 4 is connected to the common connected sources S1 and S2, and an output terminal 6 is connected to the collector 1 of the transistor 1.
  • a D.C. current is fed through the resistor 3 to the negative resistance device 2 and also to the collector-emitter circuit of the transistor 1.
  • the voltage across the terminals 31 and 32 of the negative resistance device 2 is selected to be in the range between 0 and Vt1 (i.e., positive resistance range) of FIG. 3, with the touching electrode 4 free from a contact by human body, and accordingly the negative resistance device 2 is conductive. Since the negative resistance device 2 is conductive, the transistor 1 is made conductive, making the potential of the output terminal 6 "low".
  • the potential at the output terminal 6 is raised to the source voltage in a moment, and therefore, the voltage across both terminals 31 and 32 of the negative resistance 2 is increased in a moment, to reach a voltage in the cut-off range of between Vt2 and Vt3, thereby making the negative resistance device 2 cut-off. Since the negative resistance device 2 is cut off, the transistor 1 turns off, retaining the potential of the output terminal 6 "high". This is defined as a first state, namely a reset state when the touching electrode 4 is not touched.
  • the negative resistance 2 turns “on” thereby turning the transistor 1 "on". This is defined as a second state or a switched state.
  • the abovementioned "turning on” of the negative resistance device is made because of the following reason:
  • the touching electrode 4 is touched by a human body, under the condition that both FETs 21 and 22 of the negative resistance device 2 are cut off, i.e., of high impedance, the source-drain impedance of the second FET 22 is considered to be shortcircuited by an impedance, for instance, combination of resistance and capacitance, of the human body, which impedance is far smaller than the resistance between the drain and the source of FET 22.
  • the voltage between the gate G1 connected to the drain D2 and the source S1 of the first FET 21 becomes zero, and therefore, because of the nature of a depletion mode FET, the first FET 21 turns "on". Due to this turning "on" of the first FET 21, the voltage drop between the drain D1 and the source S1 of the first FET 21 is negligible. Accordingly, the voltage between the gate G2 and the source S2 of the second FET 22 becomes nearly zero, too.
  • the second FET 22 turns “on". Due to the turns on of both FETs 21 and 22, as described in the above, the transistor 1 also turns on. By the abovementioned turning “on” of the transistor, the potential at the output terminal 6 becomes “low", thereby decreasing the voltage across both terminals 31-32 to the positive resistance range between the voltages 0 and Vt1, thereby holding the potential of the output terminal 6 "low".
  • Resetting of the switch from the abovementioned second state is made by temporarily closing the reset switch 5.
  • the circuit operates in the same way as described in the foregoing concerning the preliminary resetting.
  • FIG. 4 shows a burglar alarm system embodying the present invention, wherein, fundamental parts are similar to the example of FIG. 1 and are designated by the reference numerals and marks identical to those in FIG. 1.
  • the transistor 1 of FIG. 1 is replaced by a Darlington connection 1' consisting of a first transistor 11 and a second transistor 12, the collector of which is connected through a coil of relay 8 for actuating an alarm bell 7 to the power source E.
  • a known surge protection diode 9 for protecting the output transistor 12 from a surge current is connected across the coil of the relay 8.
  • the touching electrode 4 When the touching electrode 4 is touched by a human body, the negative resistance device, as well as the Darlington-connection 1' of the transistors 11 and 12 turns on, and therefore, the relay 8 is energized. Accordingly, the bell circuit is closed and the bell is actuated to ring. The bell continues to ring until the circuit is reset by a temporary closing of the switch 5. Therefore, by connecting the touching electrode to a steel case of a safe, a touch by a burglar actuates the alarm bell to ring.
  • the type of the transistor i.e., n-p-n or p-n-p type, should be selected responding to the polarity of the power source.
  • the transistor 1 or the composite circuit 1' of transistors may be replaced by any similar semiconductor switching device, such as a unijunction transistor, a thyristor and the like.
  • transistor(s) 1 or 1' are semiconductor devices and the resistors 3 and 13 can be made a semiconductor device too, the touch-operation switch of the present invention can be entirely semiconductorized, namely can be made as a compact monolithic semiconductor device.
  • the resetting switch 5 is connected so as to apply the source voltage to the collector of the transistor 1, in the first and the second examples, but a resetting switch can be situated in other places, for instance, in a manner to shortcircuit the base b to emitter e of the transistor 1, or to cut out the connection between the impedance element 3 to the collector c of the transistor 1 as shown by dotted lines, or the like.
  • the resistor 3 may be an alarm bell, a light-emitting diode or a small lamp, of aforementioned appropriate resistance, in order to indicate the switching by sound or by light.

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US05/546,138 1974-02-04 1975-01-31 Touch-operation switch Expired - Lifetime US3991329A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JA49-14808 1974-02-04
JP1480874A JPS5718651B2 (ko) 1974-02-04 1974-02-04

Publications (1)

Publication Number Publication Date
US3991329A true US3991329A (en) 1976-11-09

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US05/546,138 Expired - Lifetime US3991329A (en) 1974-02-04 1975-01-31 Touch-operation switch

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US (1) US3991329A (ko)
JP (1) JPS5718651B2 (ko)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4063111A (en) * 1975-11-03 1977-12-13 Steve Dobler Solid state touch switch
US4176272A (en) * 1977-11-03 1979-11-27 E-Systems, Inc. MOS-bipolar printer driver circuit
US4264072A (en) * 1978-05-26 1981-04-28 Chalmers John E Electronic game apparatus
US5489874A (en) * 1992-12-28 1996-02-06 Oki Electric Industry Co., Ltd. Inverting amplifier having negative-resistance circuit
US6388390B2 (en) 1999-04-06 2002-05-14 Erwin J. Rachwal Flashlight
US6677546B2 (en) * 2001-09-06 2004-01-13 Jung-Tsung Wei Induction control device for activating switches

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3452346A (en) * 1967-12-29 1969-06-24 Julius B Kupersmit Static charge detector
US3603811A (en) * 1969-12-09 1971-09-07 American Optical Corp Two-terminal bipolar self-powered low current limiter
US3628283A (en) * 1970-06-01 1971-12-21 Mattel Inc Electronic control device sensitive to electrostatic charge for controlling electrically operated toys and the like
US3798462A (en) * 1972-12-21 1974-03-19 A Rizzo Touch controlled switching circuit
US3805096A (en) * 1973-01-22 1974-04-16 W Hamilton Coded touch multifunction touch control switch circuitry
US3879618A (en) * 1971-11-16 1975-04-22 Magic Dot Inc Touch sensitive electronic switch

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3452346A (en) * 1967-12-29 1969-06-24 Julius B Kupersmit Static charge detector
US3603811A (en) * 1969-12-09 1971-09-07 American Optical Corp Two-terminal bipolar self-powered low current limiter
US3628283A (en) * 1970-06-01 1971-12-21 Mattel Inc Electronic control device sensitive to electrostatic charge for controlling electrically operated toys and the like
US3879618A (en) * 1971-11-16 1975-04-22 Magic Dot Inc Touch sensitive electronic switch
US3798462A (en) * 1972-12-21 1974-03-19 A Rizzo Touch controlled switching circuit
US3805096A (en) * 1973-01-22 1974-04-16 W Hamilton Coded touch multifunction touch control switch circuitry

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4063111A (en) * 1975-11-03 1977-12-13 Steve Dobler Solid state touch switch
US4176272A (en) * 1977-11-03 1979-11-27 E-Systems, Inc. MOS-bipolar printer driver circuit
US4264072A (en) * 1978-05-26 1981-04-28 Chalmers John E Electronic game apparatus
US5489874A (en) * 1992-12-28 1996-02-06 Oki Electric Industry Co., Ltd. Inverting amplifier having negative-resistance circuit
US6388390B2 (en) 1999-04-06 2002-05-14 Erwin J. Rachwal Flashlight
US6677546B2 (en) * 2001-09-06 2004-01-13 Jung-Tsung Wei Induction control device for activating switches

Also Published As

Publication number Publication date
JPS50108583A (ko) 1975-08-27
JPS5718651B2 (ko) 1982-04-17

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